1. Field of the Invention
The present invention relates to a steering angle sensor unit, attached to a steering shaft of an automobile or the like, for detecting information on rotation of a steering wheel, and for electrically connecting electric devices respectively provided in the steering wheel and a vehicle body.
2. Description of the Related Art
FIGS. 10 and 11 illustrate a conventional one of such a steering angle sensor unit. This conventional steering angle sensor unit 31 consists of a rotary connector 32 and a steering sensor 46. The rotary connector 32 comprises a stator 37, which is operative to support a first rotor 33 and a second rotor 45 connected to each other in such a manner as to be rotatable, a rotary-side lead block 34 supported by the first rotor, a stationary-side lead block 41 supported by the stator 37, and a flexible cable 44 accommodated in the stator 37.
The first rotor 33 is formed from an insulating material like a cylinder. A flange portion 33a is integrally formed like a ring in such a manner as to extend over the entire circumference of an outer wall at the top end portion of the first rotor 33. A U-shaped holding portion 33b is erected on the top surface of this flange portion 33a along an edge portion of a rectangular hole bored in a part of the flange portion 33a. A step-like portion 33c extending radially is formed on the inner circumferential wall of the first rotor 33, as illustrated in FIG. 11. A pair of engaging projections 33d are provided on the top surface of this step-like portion 33c in such a way as to be separated 180.degree., and have top end portions, each of which projects from the first rotor 33.
The rotary-side lead block 34 has a top end portion, to which a connector 36 is attached through a connecting cable 35, and has a bottom end portion attached to the first rotor 33 in such a fashion as to be protruded downwardly from the rectangular hole of the first rotor 33 and held by the holding portion 33b.
The stator 37 consists of a cylindrical cable case 38 and a disk-like lower cover 39, both of which are formed from an insulating material. A top surface plate 38a is integrally formed at the top end portion of the cable case 38 in such a manner as to extend over the entire inner circumference of the case 38 and as to have an opening 38b at the central portion thereof. The lower cover 39 has a hole 39a formed in the central portion thereof and an arcuate groove 39b opened at an end thereof to the outer circumferential portion, and is attached to the bottom end portion of the cable case 38. The hole 39a and the opening 38b of the cable case 38 face to each other and constitute a through hole 40. Moreover, the inside of the cable case 38 communicates with the outside thereof through the groove 39b. Further, the first rotor 33 is inserted from the opening 38b into this stator 37. The flange portion 33a abuts against the top surface plate 38a. Furthermore, the bottom end portion of the rotary-side lead block 34 is placed in the cable connector 38. The connecting cable 35 and the connector 36 are placed outside the stator 37.
The stationary-side lead block 41 has a top end portion, to which a connector 43 is attached through a connecting cord 42, and a bottom end portion supported by the lower cover 39 and is placed in the stator 37. Further, the connecting cord 42 and the connector 43 are led to the outside of the stator 37 through the groove 39b of the lower cover 39.
The flexible cable 44 is constituted by embedding a plurality of electrically conductive wires in flexible elongated tape in such a way as to extend in the longitudinal direction of the tape. Both end portions of any of the electrically conductive wires are exposed from the surface of the tape at both end portions of the tape. Further, this flexible cable 44 is wound around the outer circumferential wall of the first rotor 33 and accommodated in the stator 37. The flexible cable 44 has an end portion, which is supported by the bottom end portion of the rotary-side lead block 34 and electrically connected to the connector 36 through the connecting cord 35, and also has the other end portion that is supported at the top end portion of the stationary-side lead block 41 and electrically connected to the connector 43 through the connecting cord 42.
The second rotor 45 is formed from an insulating material like a cylinder, and has a top end portion, in which a claw portion 45a is integrally formed like a ring in such a way as to extend over the outer circumferential wall and in which a pair of notch portions 45b are shaped like the contour of a pen head tapered off toward the bottom end thereof and opposed to each other. Further, a flange portion 45c is integrally formed to the bottom end portion of the second rotor 45 and shaped like a ring in such a manner as to extend over the entire circumference of the outer circumferential wall. A pair of hole portions 45d are bored in this flange portion 45c in such a way as to be separated 180.degree.. Further, this second rotor 45 is inserted into the stator 37 from the hole 39a of the lower cover 39. The second rotor 45 is connected through the through hole 40 to the first rotor 33 by latching the claw portion 45a onto the step-like portion 33c of the first rotor 33 and holding the claw portion 45a. The second rotor 45 is rotatably supported by the stator 37 together with the first rotor 33 so that the flange portion 45c abuts against the bottom surface of the lower cover 39.
On the other hand, the steering angle sensor 46 comprises a rotary member 55, which connects an upper rotary member 47 to a lower rotary member 48, a stationary member 48, which supports this rotary member 55 so that this rotary member 55 can rotate, and an amount-of-rotation detecting means 51 that is supported by the stationary member 48 and adapted to detect an amount of rotation of the rotary member 55.
The upper rotary member 47 is formed from an insulating material like a cylinder. A flange portion 47a is integrally formed like a ring in such a manner as to extend over the entire circumference of an outer wall at the top end portion of the upper rotary member 47. A pair of projection portions 47b are formed on the top surface of this upper rotary member 47 in such a way as to be separated 180.degree.. Further, an extension portion 47c inwardly extending over the entire circumference of the upper rotary member 47 is formed like a ring on the bottom portion of the member 47. A pair of convex portions 47d projecting downwardly are provided on this extension portion 47c in such a manner as to be separated 180.degree.. Moreover, a ring-like projection 47e is provided in such a way as to face the inner circumferential wall of the upper rotary member 47 and to be extended from this portion 47c.
The stationary member 48 is constituted by an upper insulating case 49 and a lower insulating case 50 and formed like a cylinder. A top surface plate 49a of the upper case 49 and a bottom surface plate 50a of the lower case 50 have hole portions 49b and 50b, respectively. Further, the upper rotary member 47 is inserted from the hole portion 49b of the upper case 49 into this stationary member 48. The flange portion 47a abuts against the top surface plate 49a of the upper case 49. The extension portion 47c and the pair of convex portions 47d are placed in the stationary member 48.
The amount-of-rotation detecting means 51 comprises a disk-like code plate 52, in which a plurality of slits 52a are formed at a predetermined interval in a circumferential direction, and a detecting device 53 having a light emitting element 53a and a light receiving element 53b placed on an outer circumferential portion of this code plate 52 in such a manner as to put the slits 52a therebetween. A pair of holes 52b are formed in this code plate 52 in such a manner as to be shifted in phase at an interval of 180.degree.. Further, the amount-of-rotation detecting means 51 is placed in the stationary member 48. The pair of convex portions 47d are inserted into the pair of holes 52b of the code plate 52, respectively. The detecting device 53 is supported by the inner circumferential wall of the upper case 49.
The lower rotary member 54 is formed from an insulating material like a cylinder. A flange portion 54a is integrally formed like a ring in such a manner as to extend over the entire circumference of an outer wall at the bottom end portion of the lower rotary member 54. A pair of concave portions 54b are formed on the top surface of this lower rotary member 54 in such a way as to be separated 180.degree.. Further, this lower rotary member 54 is inserted into the stationary member 48 from the hole portion 50b of the lower case 50. The pair of convex portions 47d of the upper rotary member 47 are fitted into the pair of concave portions 54b, respectively. Thus, the code plate 52 is sandwiched between the upper and lower cases. The lower rotary member 54 is rotatably supported by the stationary member 48 together with the upper rotary member 47 by causing the flange portion 54a to abut against the bottom surface plate 50a of the lower case 50.
Furthermore, in the steering angle sensor 46 configured as described above, a coil spring 56 is put on the ring-like projection 47e. The upper rotary member 47 is placed in such a manner as to face the second rotor 45. The upper case 49 is attached to the lower cover 39 of the rotary connector 32 by using appropriate means, such as screws. Thus, the steering angle sensor unit 31 is configured by being fixed to the rotary connector 32. The pair of projections 47b are placed in the pair of hole portions 45d of the second rotor 45. The coil spring 56 compressed and sandwiched between the ring-like projection 47e and the flange portion 45c of the second rotor 45 presses the second rotor 45 and the upper rotary member 47 in a direction in which the rotor 45 becomes a little more apart from the member 47. Consequently, the flange portion 47a is a little apart from the flange portion 45c of the second rotor 45.
Next, a method of assembling this steering angle sensor unit 31 will be described hereinbelow. First, the rotary connector 32 is assembled as follows. That is, the rotary-side lead block 34, to which the connector 36 is attached through the connecting cord 35, is fitted into the holding portion 33d of the first rotor 33. Then, the first rotor 33 is inserted from the opening 38b into the cable case 38. Thus, the flange portion 33a is caused to abut against the top surface plate 38a. Subsequently, the stationary-side lead block 41, to which the connector 43 is attached through the connecting cord 42, is attached to the lower cover 39. A part, which is provided to the stationary-side lead block 41, of the connecting cord 42 is fitted into the groove 39b of the lower cover 39. Next, in the cable case 38, the flexible cable 44 is wound around the first rotor 33. Then, both end portions of the flexible cable 44 are respectively attached to the bottom end portion of the rotary-side lead block 34 and the top end portion of the stationary-side lead block 41. Thereafter, the lower cover 39 is attached to the bottom end portion of the cable case 38 by using suitable means, such as screws.
Further, when the second rotor 45 is inserted into the stator 37 from the hole 39a of the lower cover 39, the claw portion 45a formed at the top end portion of the second rotor 45 touches the step-like portion 33c of the first rotor 33. When the second rotor 45 is pushed still more into the stator 37 in this state, the claw portion 45a and the second rotor 45 inwardly bend owing to the elasticity of the second rotor 45. Furthermore, when the claw portion 45a passes through the step-like portion 33c, the claw portion 45a and the second rotor 45 are restored to an original state. Then, the claw portion 45a is caught onto the step-like portion 33c and held thereon. That is, the second rotor 45 is connected to the first rotor 33 by snap fit or stop.
In the rotary connector 32 assembled in this way, the flexible cable 44 is placed between the first rotor 33 and the second rotor 45. The flange portions 33a and 45c of the first and second rotors 33 and 45 abut against the top surface plate 38a of the cable case 38 and the bottom surface of the lower cover 39, respectively. Further, the connectors 36 and 43 are placed outside the stator 37.
On the other hand, the steering angle sensor 46 is assembled as follows. First, the detecting device 53 having the light emitting element 53a and the light receiving element 53b is supported on the inner circumferential wall of the upper case 49. Then, the code plate 52 is placed between the light emitting element 53a and the light receiving element 53b. Subsequently, the upper rotary member 47 is inserted from the hole portion 49b into the upper case 49. The extension portion 47c is made to abut against the code plate 52 by inserting the pair of convex portions 47d into the pair of holes 52b. Then, the lower case 50 and the upper case 49 are combined with each other and attached to each other by using suitable means, such as screws. Subsequently, the lower rotary member 54 is inserted from the hole portion 50b of the lower case 50 into the stationary member 48. Then, the pair of convex portions 47d are fitted into the pair of concave portions 54b. Thus, the lower rotary member 54 is attached to the upper rotary member 47.
In the steering angle sensor 46 assembled in this way, the flange portion 47a of the upper rotary member 47 abuts against the top surface plate 49a of the upper case 49. Moreover, the flange portion 54a of the lower rotary member 54 abuts against the bottom surface plate 50a of the lower case 50. Furthermore, the code plate 52 is sandwiched between the extension portion 47c of the upper rotary member 47 and the top end portion of the lower rotary member 54.
Further, thereafter, the coil spring 56 is put on the cylindrical projection 47e of the upper rotary member 47. The upper case 49 is attached to the lower cover 39 of the rotary connector 32 by using appropriate means, such as screws. Thus, the assembling of the steering angle sensor unit 31 is completed. Upon completion of assembling thereof, the coil spring 56 is compressed and sandwiched between the ring-like projection 47e and the flange portion 45c of the second rotor 45. The second rotor 45 and the upper rotary member 47 are pushed by the coil spring 56 in a direction in which the rotor 45 becomes a little more apart from the member 47.
The steering angle sensor unit 31 assembled in this way is incorporated into an automobile or the like. The stator 37 of the rotary connector 32 is fixed to a car body. The pair of engaging projections 33d of the first rotor 33 are connected to a hub of a steering shaft. Thus, the connector 36 is connected to an air bag or a horn provided on the steering wheel, while the connector 43 is connected to a drive circuit for an air bag or a horn provided on the car body. Furthermore, the detecting device 53 is used by being connected to a computer for controlling the car body. Namely, when the steering wheel is operated, the first rotor 33 rotates in response to this operation. Thus, the flexible cable 44 is wound or rewound, so that the electrical connection between the steering wheel and the car body is always maintained. The engagement between the pair of projections 47b and the pair of hole portions 45d enables the transmission of rotation of the first rotor 33 to the rotary member 55 through the second rotor 45 with the result that the rotary member 55 rotates. Thus, light emitted from the light emitting element 53a provided in the detecting device 53 is received by the light receiving element 53b through the slits 52a, so that an amount of rotation of the code plate 52 is detected. A detection signal obtained in this way is inputted to the computer provided in the car body. Then, this computer controls a suspension damping system in response to the operation of the steering wheel, and a shift position of an automatic transmission, and a rear wheel steering mechanism of a 4-wheel steering system (4WS).
However, in the aforementioned steering angle sensor unit, the rotation of the first rotor 33 is transmitted to the rotary member 55 through the second rotor 45. The first and second rotors 33 and 45 are connected to each other by snap fit. Thus, as the first rotor 33 rotates, a play between the first and second rotors 33 and 45 is caused owing to change with time. Consequently, the amount of rotation of the first rotor 33 is not equal to that of rotation of the rotary member 55. Therefore, the amount-of-rotation detecting means 51 cannot detect an operation of the steering wheel. Thus, there is a fear that the computer cannot perform the aforementioned various kinds of control operations with good precision in response to an operation of the steering wheel.
The present invention is accomplished in view of the aforementioned circumstances.